The Journal of Medical Microbiology, Vol 30, Issue 4 267-272, Copyright © 1989 by Society for General Microbiology
Cultural and electronmicroscopic studies of the effect of penicillin on tolerant oral streptococci
W. P. Holbrook, K. G. Kristinsson, A. J. Carley and S. Gunnarsdottir
Faculty of Odontology, University of Iceland, Reykjavik.
Penicillin-tolerant and -sensitive strains of oral streptococci were
treated with penicillin to determine the production of a post-antibiotic
effect (PAE). No PAE was seen with any of the S. sanguis strains tested but
most strains of the other oral streptococcal species produced a PAE.
Cultures on nitrocellulose filters treated with penicillin were examined by
scanning electronmicroscopy and showed that tolerant and sensitive strains
lost the ability to adhere to the filter after application of antibiotic.
When the filters were treated with beta-lactamase, before processing for
microscopy, the tolerant strains but not the sensitive ones recovered and
grew in a confluent lawn similar to the control cultures that had not
received antibiotic. Transmission electronmicroscopic examination of
similarly treated cultures produced comparable results. Bizarre
morphological changes were a feature of the tolerant strains of S. sanguis.
